Specifically, but not exclusively, the invention can be applied to prevent a paper jam during the formation of a stack or a group of documents (for example tickets, payment slips, receipts, coupons, vouchers, etc) printed on a continuous strip of paper and then separated from the strip itself, in particular for lottery or betting terminals.
In particular, reference is made to a stacker of a printing apparatus provided with an anti-jamming device that is suitable for preventing a jam caused by anomalous advancement of the strip due to, for example, maximum capacity of the stacker being reached or to a blockage in the stacking zone.
The prior art comprises patent publication U.S. Pat. No. 8,177,232 that shows an apparatus for stacking tickets in a ticket printer with a stacking actuator that receives the printed ticket and supplies the printed ticket to a stacking container through a main ticket exit, with a stacking diverter that guides the ticket to the correct stacking position, and with an anti-jamming device having an alternative ticket exit arranged between the actuator and the stacking diverter, in which, if the stacking container has reached maximum capacity, or if the main ticket exit is blocked, the ticket forms a loop that extends outside through the alternative ticket exit.
From patent publication EP 1676708 an anti-jamming device for printers located in public places is known, with a rise arranged in an exit conduit of the paper and with a door arranged in the zone where the paper is raised because of the rise in the event of an occlusion of the exit; the door is provided with electric contacts that are openable following lifting of the door, which lifting is actuated by the paper, to temporarily stop advancement of the paper.
One of the problems of the apparatuses of the prior art that print the documents and arrange the documents in an orderly manner in a stacking container, is the jam caused by the maximum capacity reached in the stacking container, or by any other type of occlusion near the stacking zone.
Document U.S. Pat. No. 8,177,232 proposes a solution to this problem. This solution nevertheless has some limits and drawbacks.
Firstly, an alternative ticket exit has to be provided, with resulting structural complication of the apparatus. The presence of another ticket exit, in addition to the main exit, increases the risk of intrusion of foreign bodies into the printing apparatus. Further, in the anti-jamming device disclosed in U.S. Pat. No. 8,177,232, the ticket has to form a loop that is sufficiently extended to exit through the alternative ticket exit, with the risk of incorrect operation.